Hannu Krosing wrote: > Ühel kenal päeval, L, 2007-02-17 kell 22:49, kirjutas Chad Wagner: > >> >> However, they don't have vacuum, we do. >> >> Right, and I think that is more or less because Oracle doesn't need >> it. Vacuum's main purpose (correct me if I am wrong) is to >> recover/mark rows that are no longer used, and Oracle essentially >> reuses the space immediately. >> >> Obviously with Oracle if you bloat out a table and delete a ton of >> rows then you have to rebuild the table, but that is more or less the >> same problem that PostgreSQL has and where vacuum full comes into >> play. >> >> The only benefit with the Oracle model is that you can achieve >> flashback, which is a very rarely used feature in my book. > > We can have flashbacks up to the last vacuum. It is just not exposed. > Don't vacuum, and you have the whole history. (Actually you can't go for > more than 2G transactions, or you get trx id rollover). > > To get a flashback query, you "just" have to construct a snapshot from > that time and you are done. We don't store transaction times anywere, so > the flashback has to be by transaction id, but there is very little > extra work involved. We just don't have syntax for saying "SELECT ... AS > SEEN BY TRANSACTION XXX"
Well this is certainly interesting. What do we think it would take to enable the functionality? Joshua D. Drake -- === The PostgreSQL Company: Command Prompt, Inc. === Sales/Support: +1.503.667.4564 || 24x7/Emergency: +1.800.492.2240 Providing the most comprehensive PostgreSQL solutions since 1997 http://www.commandprompt.com/ Donate to the PostgreSQL Project: http://www.postgresql.org/about/donate PostgreSQL Replication: http://www.commandprompt.com/products/ ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq